Introduction stratigraphy

Stratigraphy, a branch of geology, studies rock layers and layering (stratification). Stratigraphy, from Latin stratum + Greek graphia, is the description of all rock bodies forming the Earth's crust and their organization into distinctive, useful, mappable units based on their inherent properties or attributes in order to establish their distribution and relationship in space and their succession in time, and to interpret geologic history. Stratum (plural=strata) is layer of rock characterized by particular lithologic properties and attributes that distinguish it from adjacent layers.

History of stratigraphy begin by Avicenna (Ibn Sina) with studied rock layer and wrote The Book of Healing in 1027. He was the first to outline the law of superposition of strata:^[1] "It is also possible that the sea may have happened to flow little by little over the land consisting of both plain and mountain, and then have ebbed away from it. ... It is possible that each time the land was exposed by the ebbing of the sea a layer was left, since we see that some mountains appear to have been piled up layer by layer, and it is therefore likely that the clay from which they were formed was itself at one time arranged in layers. One layer was formed first, then at a different period, a further was formed and piled, upon the first, and so on. Over each layer there spread a substance of differenti material, which formed a partition between it and the next layer; but when petrification took place something occurred to the partition which caused it to break up and disintegrate from between the layers (possibly referring to unconformity). ... As to the beginning of the sea, its clay is either sedimentary or primeval, the latter not being sedimentary. It is probable that the sedimantary clay was formed by the disintegration of the strata of mountains. Such is the formation of mountains."

The theoretical basis for the subject was established by Nicholas Steno who re-introduced the law of superposition and introduced the principle of original horizontality and principle of lateral continuity in a 1669 work on the fossilization of organic remains in layers of sediment.

The first practical large scale application of stratigraphy was by William Smith in the 1790s and early 1800s. Smith, known as the Father of English Geology, created the first geologic map of England, and first recognized the significance of strata or rock layering, and the importance of fossil markers for correlating strata. Another influential application of stratigraphy in the early 1800s was a study by Georges Cuvier and Alexandre Brongniart of the geology of the region around Paris.

In the stratigraphy you can find term of

- Stratigraphic classification. The systematic organization of the Earth's rock bodies, as they are found in their original relationships, into units based on any of the properties or attributes that may be useful in stratigraphic work.

- Stratigraphic unit. A body of rock established as a distinct entity in the classification of the Earth's rocks, based on any of the properties or attributes or combinations thereof that rocks possess. Stratigraphic units based on one property will not necessarily coincide with those based on another.

- Stratigraphic terminology. The total of unit-terms used in stratigraphic classification.It may be either formal or informal.

- Stratigraphic nomenclature. The system of proper names given to specific stratigraphic units.

- Zone.Minor body of rock in many different categories of stratigraphic classification. The type of zone indicated is made clear by a prefix, e.g., lithozone, biozone, chronozone.

- Horizon. An interface indicative of a particular position in a stratigraphic sequence. The type of horizon is indicated by a prefix, e.g., lithohorizon, biohorizon, chronohorizon.

- Correlation. A demonstration of correspondence in character and/or stratigraphic position. The type of correlation is indicated by a prefix, e.g., lithocorrelation, biocorrelation, chronocorrelation.

- Geochronology. The science of dating and determining the time sequence of the events in the history of the Earth.

- Geochronologic unit. A subdivision of geologic time.

- Geochronometry. A branch of geochronology that deals with the quantitative (numerical)measurement of geologic time. The abbreviations ka for thousand (103), Ma for million (106), and Ga for billion (milliard of thousand million, 109) years are used.

- Facies. The term "facies" originally meant the lateral change in lithologic aspect of a stratigraphic unit. Its meaning has been broadened to express a wide range of geologic concepts: environment of deposition, lithologic composition, geographic, climatic or tectonic association, etc.

- Caution against preempting general terms for special meanings. The preempting of general terms for special restricted meanings has been a source of much confusion.

ANALYSIS SEISMIC ATTRIBUTE E1 AND E2 SAND TO IDENTIFY HYDROCARBON IN ECHO MALACCA STRAIT FIELD

PROCEEDINGS JOINT CONVENTION BALI 2007
The 32^nd HAGI, The 36^th IAGI, and The 29^th IATMI Annual Conference and Exhibition

ANALYSIS SEISMIC ATTRIBUTE E1 AND E2 SAND TO IDENTIFY HYDROCARBON IN ECHO MALACCA STRAIT FIELD

Eko Ari Prihantono², Wahyu Dwi Purnomo', M Irham N', Imam Suripto Suyanto³

¹) Lab Geofisika, Jurusan Fisika UNDIP Semarang

2) Teknik Geofisika ITB

3) Kondur Petroleum S A

ABSTRACT

Based on 3D sismic survey oil has been found in the sand stone reservoir of the Echo field malacca strait area. For eservoir management purose, the hydrocarbon discovery in this area should be follow by reservoir evaluation activities. Seismik attribute and log propoerties data has been used to identify the hydrocarbon potention in sand stone reservoir of the Echo field.

Seismik attribute prouced from the 3D seismik data exraction. Analysis hs been done to the time structure map,sesmik line attrbute and ountour map from the computtion of seismic attribute. Correlation between seismik attriute and log properties used to show the characteristic from oil reservoir

Seismic mapping shows the structural trap of anticline with the major NS trend. Attribute analysis shows the continuity of reflection characteristic in Echo field. From the correlation analysis between seismic attribute and log properties show that the hydrocarbon potention indicated by low dominant frequency range that is about 31,25 HZ – 68,34 HZ and low badwidth frequency range that is about 78,12 HZ – 85,94 HZ

Key word : seismik attribute, log properties, dominant frequency, bandwidth frequency

MAGNETIC EVOLUTION OF THE DIENG VOLCANIC COMPLEX, CENTRAL JAVA

PROCEEDINGS JOINT CONVENTION BALI 2007
The 32^nd HAGI, The 36^th IAGI, and The 29^th IATMI Annual Conference and Exhibition

MAGNETIC EVOLUTION OF THE DIENG VOLCANIC COMPLEX, CENTRAL JAVA

Haryo Edi Wibowo^1
1Department of Geological Engineering Gajah Mada University, Yogyakarta
ABSTRAK

The Dieng volcanic complex (DVC) that is situated in Central Java, consists of many volcanic edifices inside and around the caldera structure representing a series of island arc magmatism activities. Radiometric dating reveal that the activities take place from 3.60 Ma to 0.06 Ma or from Pliocene to Recent. This enables us to study evolution of magma in a volcanic complex temporally. This study would be useful to enhance knowledge about volcanic related resources exploration such as gold deposit which quite common in tertiary volcanism.

In order to understood magma evolution in DVC therefore, field geologic observation and rock sample collection from different volcanic edifices of different periods were conducted. In addition, satellite image analysis was conducted to generate a volcanic edifice distribution map. Furthermore, rock samples were analyzed using thin section observation and whole-rock petrochemical compositions analyses to study petrogenesis of magmas.

The analyses result in the spatial and temporal geochemical evolution of volcanic edifices within the DVC. Generally, the volcanic rocks alkalinity increases gradually from the oldest edifice (i.e. G. Kendang-Prahu; 3.6 to ~2.5 Ma) to the youngest ones (i.e. G. Kendil-Sikunir). From the oldest to the youngest volcanoes, the magmatic affinities change from the medium K into the upper limit of high K class. K2O and Rb data show that DVC, except the Prahu volcano, gradually change its status from the trench-side volcanism during the Pliocene-Pleistocene into the backarc-side volcanism during the Pleistocene-Recent. The trends of major oxides versus silica contents show that magmas underneath DVC experienced fractional crystallization and crust contamination for each volcanism event, especially advanced differentiation among the pre caldera volcanism. The presence of large eruption crater within most of the pre caldera volcanoes and dacitic volcanism among them are identical with explosive eruption events that most likely had caused the caldera collapse. Following major magmatic evolution events are identified. First, the source of DVC magmas are generally from the partial melting of peridotite mantle which is represented by basalt as primitive magma. The low Ni content indicates that the basalt as primitive magma already experienced contamination. Second, the geologic setting of DVC changes from a trench-side magmatism during the Pliocene into a backarc-side magmatism during the Quaternary. Third, caldera-forming eruptions took place when the DVC setting was on the trench-side and when the advanced differentiation process took place.

THE EXISTANCE OF MINERAL GOLD DEPOSIT ZONE USING INDUCED POLARIZATION METHOD AT MUARA MANDERAS, JAMBI

PROCEEDINGS JOINT CONVENTION BALI 2007
The 32^nd HAGI, The 36^th IAGI, and The 29^th IATMI Annual Conference and Exhibition

THE EXISTANCE OF MINERAL GOLD DEPOSIT ZONE USING INDUCED POLARIZATION METHOD AT MUARA MANDERAS, JAMBI

Feisal Dirgantara¹, Joko Hariyadi²

¹Lab.Geofisika, Jurusan Fisika FMIPA, Universitas Gadjah Mada
²PT Aneka Tambang Unit Geomin, Pulogadung, Jakarta Timur

ABSTRACT

A geophysical survey using induced polarization method was carried out in Muara Manderas, Jambi. This research aimed to determine the existence of mineral gold deposit of the research area based on induced polarization data analysis. Data acquired using IP Yokohama LF 82 receiver-transmitter and Global Positioning System (GPS) during 21 days, which cover an area of 0,5 km x 1 km. The measurement spacing was 25 – 50 m.

Raw data processing was performed using IP measurement of frequency domain. Apparent resistivity data shows the liquid content of rock formation. Percent frequency effect shows the mineral alteration content of rock formation. Quantitative interpretation was done by cross section anomaly modeling based on Surfer 8.0.

From the XRD test laboratory, geochemical test and geological traversing, the mineral gold deposit was performed as argilic. By using induced polarization, argilic was determined as low apparent resistivity and high percent frequency effect. It was showed that argilic has the most spacious deposit at the regional structure in line SM 0 and SM -100, while small deposit at the local structure also appeared in line SM -500.

PRESTACK INTERCEPT & GRADIENT SCALING TO THE MODELED SYNTHETIC AN EXAMPLE FROM HEIDRUN FIELD, NORTH SEA

PROCEEDINGS JOINT CONVENTION SURABAYA 2005 – HAGI-IAGI-PERHAPI
The 30^th HAGI, The 34^th IAGI, and The 14^th PERHAPI Annual Conference and Exhibition

PRESTACK INTERCEPT & GRADIENT SCALING TO THE MODELED SYNTHETIC
AN EXAMPLE FROM HEIDRUN FIELD, NORTH SEA

Nguyen Nam
Landmark Graphics, Kuala Lumpur, Malaysia & Larry Fink, Landmark Graphics, Denver, USA
ABSTRACT

Calibration is the key to successful amplitude vs. offset (AVO) analysis to identify fluid and lithology changes using prestack seismic data. A common AVO crossplot shows the attributes of “intercept” and “gradient” help to separate different lithologies and/or fluids. To move from qualitative anomaly analysis of prestack to quantitative analysis–classifying how oil, gas, or brine appear on the pre stack data–it is necessary to scale the real data to the modeled synthetic data. In this paper, we consider a scaling process that matches the magnitudes of intercept and gradient events extracted from the real data to the intercept and gradient of the modeled data. A case study is presented, demonstrating this process of matching real prestack gathers to the log-generated gathers in a 2D crossplot. The scaled data are then used to compare anomalous intercept-gradient data points that represent lithologic and/or pore fluid changes from the background data throughout the entire 3D survey.